The invention relates to a surveillance sensor which is provided with at least one surveillance radar antenna rotatable about at least one first axis of rotation.
An embodiment in which such a surveillance radar antenna rotates about a vertically oriented axis of rotation at a fixed rotation rate, has the disadvantage that the information obtained by such an antenna is limited to azimuth and range data of the detected objects. However, for tracking a moving object by means of a surveillance radar antenna or for controlling a tracking radar which is to track an object detected by the surveillance radar antenna, it is advantageous to have the disposal of additional elevation data of the object. Indeed, additional elevation data may be obtained by a so-called phased-array surveillance antenna, but the disadvantage of this antenna is that it is expensive and complex. An further disadvantage is that even a radar, capable of providing information concerning the speed of detected objects on the basis of the Doppler effect, has trouble detecting stationary or slowly moving objects in a high-clutter environment, e.g. helicopters above land.